If you find yourself in crisis and cannot afford food, try to contact a local church, mosque, synagogue, gurdwara or other religious place of worship, they will likely offer support to you regardless of your faith, your local community centre or your medical surgery can also help, and you can likely contact any of them either by phone or online. These organisations may be able to refer you to a local foodbank, or you may simply be able to attend one no questions asked, but this can differ between providers, so make sure to check their website first.
Here's a few helpful resources: